A recombinant peptide antigen line immunoassay optimized for the confirmation of Chagas' disease

BACKGROUND: The transfusion of contaminated blood has become the major route of transmission for Chagas' disease in Brazil. Current screening tests are insensitive and yield conflicting results, while confirmatory assays do not exist. A line immunoassay (INNO‐LIA Chagas Ab [INNO‐LIA]) combining relevant, immunodominant recombinant and synthetic antigens on a single nylon membrane strip was evaluated for the serologic confirmation of Chagas' disease. STUDY DESIGN AND METHODS: Sera from 1062 patients and healthy residents of four Brazilian regions endemic for Chagas' disease were used for test optimization. The established confirmation algorithm was evaluated with an independent set of positive (n = 75) and negative (n = 148) samples. RESULTS: In the optimization phase, without an established comparative gold standard, the results with the INNO‐LIA were compared with those obtained in four other screening assays. In the validation phase, the INNO‐LIA showed a sensitivity of 100 percent (95% CI, 95.21‐100) and a specificity of 99.32 percent (95% CI, 96.29‐99.98) for well‐characterized sera. Moreover, its specificity reached 100 percent with a set of 40 sera obtained from patients with documented leishmaniasis. The interpretation criteria defined in this study indicated that the INNO‐LIA accurately detected the presence of antibodies to various specific antigens of Trypanosoma cruzi. CONCLUSION: The INNO‐LIA Chagas Ab assay may become the first commercial assay to reliably confirm the presence of antibodies to T. cruzi.